How to flash ROM1.Copy
ROM.zip
and Firmware.zip to phone (via MTP mode or just into
your SD-Card) and just flash ROM and then Firmware via
TWRP>Install zip
2.After first boot, open Ultimate Control app to let him
get ROOT access and go to Magisk Manager > Modules
and install them from _MagiskModules folder on your
internal memory (only if you are ROOT'ed)

How to update ROM1.Copy
ROM.zip
to phone (via MTP mode or just into your SD-Card) and
just flash it via TWRP>Install zip
2.Flash it as always just with select "Dirty flash
(update)" option in Aroma instead of "Full wipe (clean
install)"3.You can update also firmware
(bootloader and modem) and kernel if new ones
are out, just flash Firmware.zip or Kernel.zip
same as any other one
*.Don't forget to flash latest Magisk.zip
after update kernel if you were ROOT'ed!

HERE
is list all CSC's which are available by default in
Ultimate ROM with explanation of codes

How to change CSC for SIM2 (DualSIM):
1.Do backup of your EFS partition via TWRP and copy to
safe place on your PC (best) or just SD!
2.Download MiXplorer (app) HERE
3.Go to /efs/imei and open omcnw_code2.dat file
4.Change three letters to CSC which you want to set and
save then reboot phone